Major changes to improve the safety of North Sea helicopter operations, including prohibiting flights in the most severe conditions, have been announced by aviation regulators.

The changes include amendments to the seating of passengers, improved breathing equipment, changes to pilots' training and equipment improvements.

Announced by the Civil Aviation Authority (CAA), the measures follow a series of North Sea helicopter crashes in recent years including last August's Super Puma tragedy in which four people died and the April 2009 Super Puma disaster which claimed 16 lives.

The changes are the result of a comprehensive review of offshore helicopter operations undertaken in conjunction with the Norwegian CAA and the European Aviation Safety Agency (EASA) and advised by a panel of independent experts.

The measures include:

:: Prohibiting helicopter flights in the most severe sea conditions, so that the chance of a ditched helicopter capsizing is reduced and a rescue can be safely undertaken;

:: Pending further safety improvements to helicopters, passengers will only be able to fly if they are seated next to an emergency window exit to make it easier to get out of a helicopter in an emergency (unless helicopters are fitted with extra flotation devices or passengers are provided with better emergency breathing systems);

:: Requiring all passengers to have better emergency breathing equipment to increase underwater survival time unless the helicopter is equipped with side floats.

Also, there will be important changes to the way pilots are trained and checked. And the CAA will take on the role of approving each offshore helideck, ensuring they meet strict safety standards.

The CAA has made a number of recommendations to EASA, as the regulator for helicopter certification and airworthiness. These include enhancing the safety of helicopters; establishing a review of offshore helicopter accidents and incidents with national aviation organisations, such as the CAA, to highlight safety issues and develop remedies; and the development of standardised helicopter operating information for pilots.

In the meantime, the CAA is expecting helicopter operators to make improvements to helicopters and survival equipment including:

CAA chair Dame Deirdre Hutton said: "The safety of those who rely on offshore helicopter flights is our absolute priority. The steps we are announcing today will result in significant improvements in safety for those flying to and from offshore sites in the UK and potentially worldwide."

She went on: "We expect helicopter operators, the oil and gas industry and EASA to move forward with recommendations to them as soon as possible.

"For our part, the CAA is already taking forward actions directly under our control. We will monitor and report regularly on progress, so that people can have confidence that these important changes are being implemented as quickly as possible."

In gathering evidence for the review the CAA team engaged with trade unions representing industry workers and pilots, the oil and gas industry, helicopter operators, manufacturers, government, regulatory bodies and other experts in the field, as well as analysing available data and reports.

While each organisation will be accountable for implementing the recommendations under their control, the CAA will establish and chair a new safety forum that will actively promote delivery of the recommendations and publicly report on progress.

In last August's accident, a Super Puma helicopter with 16 passengers and two crew aboard crashed into the sea on approach to Sumburgh airport in the Shetland islands. Four of the passengers were killed.

In May 2012, all 14 passengers and crew members on a Super Puma helicopter were rescued after it ditched about 30 miles off the coast of Aberdeen. It was on a scheduled flight from Aberdeen to a platform in the North Sea.

In October 2012, all 17 passengers and two crew escaped injury when their helicopter ditched in the North Sea en route from Aberdeen to a rig 86 miles out.

On April 1, 2009, 16 people died when a Super Puma plunged into the sea off the Aberdeenshire coast. The gearbox of the Bond-operated helicopter failed while returning from the BP Miller platform.

The tragedy came after a February 18, 2009 incident when another Bond Super Puma with 18 people on board ditched in the North Sea as it approached a production platform owned by BP. Everyone survived that incident.

Frank Doran, Labour MP for Aberdeen North said: " I welcome the CAA report. It is a useful examination from the point of view of the regulator into some of the problems, issues and future requirements for the offshore helicopter transport service.

"I particularly welcome the comments made in relation to ditching requirements. The comparison with the Norwegian system of management of helicopter transport is welcome, but the action suggested by the report raises other questions. The Norwegian system has a direct link to the transport ministry as well the Norwegian CAA. That gives much more muscle to the reporting system.

"Also the establishment of this new committee poses the question of the need for the Helicopter Safety Transport Group, an oil and gas industry body."

Jim McAuslan, general secretary of pilots' union Balpa, said: "The hundreds of dedicated helicopter pilots flying in support of Britain's oil and gas industry and ferrying people to offshore rigs welcome these proposals which will help them make every single flight a safe flight.

"Pilots will work with the CAA and operators to improve helicopter safety in the North Sea and ensure there is no backsliding as memories of recent accidents fade."

He went on: "The CAA has recognised that independently setting and protecting decent helicopter flight safety standards in the North Sea is more effective than a 'light touch' approach.

"Pilots particularly welcome the ban on flying in adverse conditions and the recommendations on how the chances of surviving an incident can be improved. We will work closely with all concerned to make sure such changes are effective.

"Today's report will need to be seen alongside reports due from the (House of Commons) Transport Select Committee on offshore helicopter safety, Air Accidents Investigation Branch reports and fatal accident inquiries and we maintain our call for an independent inquiry to bring all of this work together."

Shadow transport secretary Mary Creagh said: "This report is a wake-up call to the oil and gas industry about the need to improve the safety culture of helicopter operations in the North Sea.

"Avoiding flights in storm conditions, installing on-board safety equipment, and extending CAA regulation to heliports should all help significantly to avoid further tragedies in the North Sea."

Shadow Scottish secretary Margaret Curran said: "Since 1992, 51 people have died as a result of helicopter accidents in the North Sea. This review was long overdue and we welcome its findings.

"The oil and gas industry is vital for Scotland and for the thousands of people who work in the North Sea. The CAA, the industry and trade unions now need to work together to implement the recommendations."

Bob Crow, general secretary of the RMT union, said: "The CAA's review is a step toward the improvements that we have supported for years.

"We support the recommendations as far as they go but cannot see how they are going to be enforced when the number of CAA helicopter inspectors is being cut."

Mr Crow went on: "An opportunity has been missed here for actions that would improve the confidence of our members in the safety of offshore helicopters, including the system of reporting of incidents and accidents which the review completely ignored.

"We need to know more from the CAA on exactly how they intend to enforce these recommendations and we continue to demand a public inquiry into the offshore oil and gas industry as a whole, including offshore helicopter operations."